References:

Proceedings
of a Symposium on "The Optical Telegraph" (Stockholm, June 21-23 1994)
- the URL
for this resource seems to be no longer available from Stockholm's Tekniska
Museet.

Synchronous Telegraph Experiments (1790-1791)

"... The brothers Chappe spent the
winter
of 1790-1791 experimenting with telegraph designs. In March 1791, they
were ready for a first public demonstration of the telegraph they had
constructed.
The telegraph design used in this first experiment was described by the
Chappes as a "pendulum system." It is usually referred to as the
SynchronizedSystem.

"For the first experiments, two telegraphs
were
used, possibly merely two modified pendulum clocks. One was placed on a
terrace at the former location of a castle in Chappe's hometown
Brûlon,
and the other at the window of a private house in Parcé, a
little
town at a distance of roughly 16 km (10 miles), and about halfway
between
Brûlon and La Flèche. ....

"Unfortunately, we do not have an
accurate
description of the working of the pendulums that were used in the first
experiment, and the information we have leaves many questions
unanswered.
The most reliable record that has survived is a description given by
Ignace
Chappe, which reads as follows.

The first telegraphic
correspondence
that we performed was done with two pendulum clocks, that were kept in
perfect synchrony; the face of the clocks was divided into ten parts,
each
part designating a different numeral [French: un chiffre de la
numération
ordinaire]. When the pointer of one clock passed over the number one
wanted
to indicate, a sound was made, announcing to the correspondent that the
number which also his pointer indicated at the moment that the sound
was
heard, was significant. By representing the words in a dictionary
with successive numbers one could thus transmit any thought. ..."

Panel Telegraph Experiments (1792)

"... Not satisfied with the use of
the
pendulum system, Chappe had started experimenting with a different
design.
He built a rectangular wooden frame with five sliding panels (in French
persiennes) that could be displayed or obscured individually with
pulleys.
The five panels trivially produced a five-bit binary code, with 25
or 32 possible combinations, more than three times as many codes as
used
in the first design...."
(Source)

An
example of a panel system: Early (1794) Model of
Lord George
Murray'sSix-Shutter
Telegraph Design. (Coll.
Victory Museum, England)

Semaphore Telegraph System (1793...)

"...
Around this time Claude Chappe concluded that the
panel
telegraph had been a false start, and he changed designs once more. As
Ignace noted:

Some time later [we] established with certainty that
elongated
objects were better visible than the sliding panels adopted before.

"The semaphore telegraph that Chappe designed next consisted of a large
horizontal beam, called a regulator, with two smaller wings, called
indicators,
mounted at the ends, seemingly mimicking a person with
wide-outstretched
arms, holding a signal flag in each hand. The angles of the indicators,
andindependently also the position of the large regulator beam, could
be
varied in increments of 45 degrees, sufficient for the encoding of
hundreds
of symbols, ..." (Source)